ADC3908S025: Using resistor divider in the input of ADC to reduce full scale voltage

Dileep P

Part Number: ADC3908S025
Other Parts Discussed in Thread: LMH6881

Tool/software:

Hi,

I am using an ADC to convert the 3MHz sinusoidal signal coming from a sensor to ADC3908S025IRSMT input. The sensor signal is processed using a PGA LMH6881, but the minimum supply for PGA is 5V. Single ended full scale input of ADC is 0.95V. I am planning to use a simple resistor divider in front of ADC for conversion, but there are no mention of current requirement ADC pins. I want to select the resistors such that it doesn't affect the ADC performance. Can you help me to select the resistors?

4 months ago

0 Rob Reeder 4 months ago

TI__Mastermind 40770 points

Hi Dileep,

In order to make sure I understand what you are planning to do, can you please send me a block diagram or schematic?

Do you want to DC couple the LMH to the ADC? Or AC couple? I assume DC couple based on what you said above, but please confirm.

I can help you once I have this understanding from you.

Regards,

Rob

0 Dileep P 4 months ago in reply to Rob Reeder

Prodigy 20 points

Hi Rob,

The circuit is simple, it is a DC coupled connection. The signal is always above 0V and the ADC is AVDD is 1.8V. If my understanding is correct, then For ADC maximum swing is +/-0.95V. So I want a voltage divider circuit between them.